FIELD
[0001] The present disclosure relates generally to composites and, more particularly, to
optically transparent reinforced composite articles.
BACKGROUND
[0002] Glass is widely used as a transparency in a variety of applications due to its superior
optical qualities. For example, glass is commonly used as glazing material or as an
architectural material for buildings. Glass is also commonly used as a transparency
in a variety of vehicular applications. Unfortunately, glass is a relatively dense
material and is also relatively brittle such that relatively large thicknesses are
required to provide the glass with sufficient strength to resist shattering when impacted
by an object.
[0003] In an attempt to avoid the weight penalties associated with glass, transparencies
may also be fabricated of polymeric material. For example, transparencies may be formed
of transparent polymers such as acrylic (e.g., Plexiglas
™) which is less dense than glass and which possesses suitable optical properties.
Unfortunately, acrylic has relatively low strength properties making it unsuitable
for many applications where high impact resistance is required.
[0004] In consideration of the weight penalties associated with glass and the strength limitations
associated with transparent polymers, manufacturers have fabricated transparencies
from polymeric materials reinforced with glass fibers to enhance the strength and
impact resistance of the polymeric transparency. Unfortunately, the addition of glass
fibers to polymeric material may undesirably affect the optical quality of the transparency.
For example, the glass fibers may have a cylindrical configuration such that each
one of the glass fibers acts as a small lens. The effect of a plurality of the glass
fibers, each acting as a small lens, is a scattering of light as the light passes
through the transparency such that objects viewed through the transparency may appear
blurred.
[0005] A further drawback associated with transparencies fabricated from glass fiber-reinforced
polymeric materials is the variation in the refractive indices of the glass material
and polymeric material as temperature changes. Refractive index, represented by n(λ,T),
is a function of wavelength λ incident on a material at temperature T. In the case
of glass fiber-reinforced polymeric materials, the refractive index of the polymeric
material generally decreases with increasing temperature for a given wavelength or
wavelength band such as the visible spectrum. In contrast, the refractive index of
glass typically varies only slightly with changes in temperature for the visible spectrum.
[0006] Such a change in refractive index of a material with temperature change of a material
for a given wavelength may also be defined as the temperature coefficient of refractive
index of the material, dn(λ,T)/dT. In the expression dn(λ,T)/dT, dn represents the
change in refractive index of the material, λ represents the wavelength of radiation
(e.g., light) incident on the material, T represents temperature, and dT represents
the change in temperature of the material. It should be noted that although a material
may be described in terms of its refractive index at one or more wavelengths and temperatures,
the temperature coefficient of refractive index of a material is also typically listed
with the refractive index data for the material.
[0007] Although glass and polymeric material may be selected to have the same refractive
index at a given match point temperature for a given wavelength, the differences in
temperature coefficient of refractive index dn(λ,T)/dT of the glass as compared to
the temperature coefficient of refractive index dn(λ,T)/dT of the polymeric material
results in a change (e.g., an increasing difference) in the refractive indices of
the two materials as the temperature diverges from the match point temperature. The
change in refractive indices of the glass and polymeric material as temperature changes
may result in a corresponding reduction in optical quality of the transparency with
change in temperature due to scattering of light at the glass/polymer interface.
[0008] As can be seen, there exists a need in the art for an optically transparent composite
article which has a relatively high degree of optical transparency with minimal optical
distortion within a relatively broad temperature range and which exhibits improved
ballistic and mechanical performance with minimal weight.
[0009] WO 02/074533 describes a composite formed of a polymer matrix phase having a reinforcement phase
including polymeric microfibers. The microfibers are preferably formed of a highly
oriented polymer, having a high modulus value and a large surface area. The large
surface area can serve to tightly bind the microfibers to the polymer matrix phase.
The microfibers can be provided as a fully- or partially-microfibrillated film, as
a non-woven web of entangled microfibers, or as a pulp having free fibers. The microfibers
can be embedded in, or impregnated with, a polymer or polymer precursor. Some composite
articles are formed from thermoset resins cured about a highly oriented poylpropylene
microfiber reinforcement phase, providing a strong, tough, moisture resistant article.
One composite includes a matrix and reinforcement formed of the same material type
and having substantially equal refractive indices, allowing the composite to be optically
clear.
[0010] US 2008/0241537 describes a transparent, reinforced, composite polymeric fiber that has a polymeric
body portion made from a first thermoplastic polymer that is transparent to visible
light. The fiber includes polymeric reinforcement elements embedded within the polymeric
body portion. The polymeric body portion extends between and about the polymeric reinforcement
elements. Each polymeric reinforcement element is formed from a second thermoplastic
polymer that is transparent to visible light. The peripheral portion and outer surface
of the polymeric body portion defines a peripheral portion and outer surface, respectively,
of the transparent, reinforced, composite polymeric fiber. A plurality of the fibers
are formed into an array that is processed with a consolidation process to form a
transparent, reinforced, composite structure.
[0011] In
US 2006/0193577, a polarizer is formed with an arrangement of polymer fibers substantially parallel
within a polymer matrix. The polymer fibers are formed of at least first and second
polymer materials. At least one of the polymer matrix and the first and second polymer
materials is birefringent, and provides a birefringent interface with the adjacent
material. Light is reflected and/or scattered at the birefringent interfaces with
sensitivity to the polarization of the light. In some embodiments, the polymer fibers
are formed as composite fibers, having a plurality of scattering polymer fibers disposed
within a filler to form the composite fiber. In other embodiments, the polymer fiber
is a multilayered polymer fiber. The polymer fibers may be arranged within the polymer
matrix as part of a fiber weave.
[0012] US 2008/0145638 describes transparent composite article comprising a polyurethane matrix and incorporated
within the matrix nanofibers having a diameter up to 5000 nanometers.
BRIEF SUMMARY
[0013] According to a first aspect of the invention, there is provided a composite article
as recited in claim 1.
[0014] According to a second aspect of the invention, there is provided a method of manufacturing
a composite article as recited in claim 8.
[0015] The above-described needs associated with transparent composite articles are specifically
addressed and alleviated by the present disclosure which, in an embodiment, provides
a substantially optically transparent composite article comprising a substantially
transparent matrix and at least one substantially transparent organic fiber embedded
within the matrix. The fiber has a refractive index that is substantially equivalent
to the matrix refractive index within a wavelength band of interest.
[0016] In a further embodiment, disclosed is a substantially transparent composite article
providing favorable optical transmission characteristics and minimal distortion. The
composite article may comprise a substantially transparent matrix and a plurality
of substantially transparent organic fibers embedded within the matrix. The fibers
may have a refractive index that is substantially equivalent to the matrix refractive
index within a wavelength band of interest. The matrix and the organic fiber may also
have substantially equivalent temperature coefficients of refractive index. The temperature
coefficient of refractive index represents change in refractive index of the material
with change in temperature of the material.
[0017] In a further embodiment, disclosed is a methodology of manufacturing a composite
article comprising one or more of the steps of selecting a wavelength band of interest
and providing a substantially transparent matrix having a matrix refractive index.
The method may additionally include providing at least one substantially transparent
organic fiber having a refractive index that is substantially equivalent to the matrix
refractive index within the wavelength band of interest. The method may further include
embedding the organic fiber within the matrix.
[0018] In a further embodiment, disclosed is a methodology of manufacturing a composite
article comprising one or more of the steps of selecting at least one of a visible
spectrum and an infrared spectrum as a wavelength band of interest to which the composite
article is to be subjected. A temperature range may be selected to which the composite
article is to be subjected. The method may include providing a substantially transparent
matrix having a matrix refractive index and a temperature coefficient of refractive
index. A plurality of substantially transparent organic fibers may be provided wherein
the organic fibers have a refractive index and a temperature coefficient of refractive
index. The temperature coefficient of refractive index of the fibers is substantially
equivalent to the temperature coefficient of refractive index of the matrix within
the temperature range. The refractive index of the fibers may be substantially equivalent
to the matrix refractive index within the wavelength band of interest. The method
may further include the step of providing the organic fibers in an elongated cross
section having an opposing pair of substantially planar fiber faces and embedding
the organic fibers within the matrix to form at least one layer of organic fibers
within the matrix. The substantially planar fiber faces of the organic fiber may be
oriented to be substantially parallel to a substantially planar article surface of
the composite article.
[0019] The features, functions and advantages that have been discussed can be achieved independently
in various embodiments of the present disclosure or may be combined in yet other embodiments,
further details of which can be seen with reference to the following description and
drawings below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] These and other features of the present disclosure will become more apparent upon
reference to the drawings wherein like numerals refer to like parts throughout and
wherein:
Figure 1 is a perspective illustration of a composite article in an embodiment comprising
substantially transparent polymeric matrix and a plurality of substantially transparent
organic fibers;
Figure 2 is an exploded perspective illustration of the composite article of Figure
1 and illustrating a plurality of layers of the organic fibers;
Figure 3 is an enlarged perspective illustration of a portion of the composite article
of Figure 1 and illustrating the arrangement of the layers of organic fibers within
the matrix;
Figure 4 is an enlarged sectional illustration taken along line 4-4 of Figure 3 and
illustrating an embodiment of the organic fibers having a generally elongated cross-sectional
shape;
Figure 5 is a graph of refractive index at a given wavelength versus temperature and
illustrating the substantially equivalent refractive indices of polymeric matrix and
organic fiber within a temperature band and further illustrating the mismatch between
the refractive indices of the polymeric matrix and glass fiber with changing temperature;
Figure 6 is a graph of strength versus stiffness (i.e., modulus of elasticity) for
composite articles having organic fibers in a cross-ply configuration and further
illustrating strength versus stiffness for a composite article comprised of glass
fibers in a cross-ply configuration; and
Figure 7 is an illustration of a flowchart of one or more operations of a methodology
of manufacturing a composite article.
DETAILED DESCRIPTION
[0021] Referring now to the drawings wherein the showings are for purposes of illustrating
preferred and various embodiments of the disclosure, shown in Figure 1 is an embodiment
of a composite article 10. The composite article 10 may be fabricated as a fiber-reinforced
composite panel 14 comprising a substantially transparent polymeric matrix 16 and
a plurality of substantially transparent organic fibers 18 embedded within the polymeric
matrix 16. Although illustrated in Figure 1 in a panel 14 configuration, the composite
article 10 may be provided in any one of a wide variety of sizes, shapes and configurations,
without limitation, and may include planar and/or compound surfaces.
[0022] Referring to Figure 4, the organic fibers 18 of the composite article 10 are embedded
within the polymeric matrix 16 and are preferably shaped to have at least one substantially
flat or planar fiber face 20 or, more preferably, an opposing pair of substantially
flat or planar fiber faces 20. However, the organic fibers 18 may be provided in any
one of a variety of alternative shapes and sizes including single curvatures (not
shown) on any one of the fiber faces 20 of the organic fibers 18. The combination
of substantially transparent polymeric matrix 16 and substantially transparent organic
fibers 18 results in a substantially transparent composite article 10 that facilitates
transmission of radiation or light in any wavelength that is incident 24 on the composite
article 10 as illustrated in Figure 4. For example, the matrix 16 and the organic
fibers 18 may be selected to facilitate the transmission of radiation in the visible
spectrum and/or radiation in the infrared spectrum through the composite article 10.
[0023] Advantageously, the matrix 16 and the organic fiber 18 preferably have complementary
or substantially equivalent refractive indices within a broad temperature range for
a wavelength band of interest. The refractive index of a given material at a given
temperature T may be defined as the ratio of the speed of light at a given wavelength
λ in a vacuum to the speed of light at the same wavelength λ in the given material
at the given temperature T. The refractive indices of the matrix 16 and the organic
fiber 18 are preferably substantially equivalent or closely matched within a wavelength
band of interest for a given temperature range in order to minimize or reduce scattering
of light or radiation at the interface of the matrix 16 with the organic fiber 18.
Such scattering of light may otherwise occur at the interface of matrix and fiber
having substantially different refractive indices. In the presently disclosed embodiments,
the substantially equivalent refractive indices of the matrix 16 and the organic fiber
18 may facilitate a relatively high degree of optical transmission and low distortion
of radiation through the composite article 10 and may effectively expand the useful
operating temperature of the composite article 10.
[0024] Referring still to Figure 4, the matrix 16 and organic fiber 18 may also be defined
as having substantially equivalent temperature coefficients of refractive index dn(λ,T)/dT
wherein dn(λ,T)/dT is the partial derivative of n(λ,T) with respect to temperature
T. As indicated above, the temperature coefficient of refractive index dn(λ,T)/dT
of a material may be defined as the change in refractive index of the material for
a given wavelength with change in temperature of the material. Although the matrix
16 and the organic fiber 18 of the present disclosure are described as preferably
having substantially equivalent refractive indices within a broad temperature range
for a wavelength band of interest, the matrix 16 and the organic fiber 18 may be described
in terms of having substantially equivalent temperature coefficients of refractive
index as the temperature coefficient of refractive index of a material is typically
listed in available literature with the refractive index data for the material.
[0025] In the present disclosure, the polymeric matrix 16 and the organic fiber 18 preferably
have substantially equivalent refractive indices within a broad temperature range
for a wavelength band of interest such that the respective temperature coefficients
of refractive index are also substantially equivalent. In an embodiment, the temperature
coefficients of refractive index for the polymeric matrix 16 and the organic fiber
18 may be such that the refractive indices of the polymeric matrix 16 and the organic
fiber 18 correspond to substantially similar rates of decrease in the refractive indices
of the matrix 16 and the organic fiber 18 for a given wavelength as temperature increases.
The advantages provided by the substantially equivalent refractive indices and substantially
equivalent temperature coefficients of refractive index of the matrix 16 and organic
fiber 18 include improved optical transparency of the composite article 10 with minimal
distortion within a relatively broad temperature range as described in greater detail
below.
[0026] Referring to Figure 1, shown is the composite article 10 formed as a panel 14 and
comprising a plurality of organic fibers 18 formed of organic, polymeric matrix 16
and wherein the organic fibers 18 are embedded within the polymeric matrix 16. The
organic fibers 18 may comprise structural reinforcing for the substantially transparent
polymeric matrix 16 and may improve the mechanical performance of the composite article
10. For example, the structural reinforcing provided by the organic fibers 18 may
improve the specific stiffness of the composite article 10 (i.e., stiffness of the
composite article 10 divided by the density) due to the enhanced tensile strength
and modulus of elasticity of the organic fibers 18 as described in greater below.
[0027] Referring to Figure 2, shown is an exploded illustration of the panel 14 of Figure
1 and illustrating a plurality of the organic fibers 18 formed as strips and arranged
in layers 32 within the matrix 16. Each one of the organic fibers 18 preferably has
an elongated cross-sectional shape preferably including an opposed pair of substantially
planar fiber faces 20. In an embodiment, the fiber faces 20 of the organic fibers
18 may be arranged to be substantially parallel to the composite article surface 12
to enhance the optical performance of the composite article 10 in a manner as described
in greater detail below.
[0028] Referring to Figure 3, shown is an enlarged perspective illustration of the composite
article 10 wherein the organic fibers 18 are arranged in layers 32 within the matrix
16 of the composite article 10. The organic fibers 18 may be arranged in any orientation
relative to one another within the composite article 10 and are not limited to the
arrangement shown in Figure 3 wherein the organic fibers 18 in each one of the layers
32 are aligned with one another in substantially parallel relationship. Although the
composite article 10 is illustrated as having three of the layers 32 of organic fibers
18, any number of layers 32 may be provided. For example, the composite article 10
may contain a single layer 32 of organic fibers 18 or tens or more of the layers 32.
[0029] The organic fibers 18 in one or more of the layers 32 may be oriented in any manner
relative to the other organic fibers 18 in the composite article 10 including, but
not limited to, unidirectional arrangements wherein the lengths of the organic fibers
18 in a layer 32 are oriented generally parallel to one another. The organic fibers
18 may also be oriented in a bidirectional arrangement or a cross-ply configuration
wherein the organic fibers 18 in a layer 32 are oriented generally perpendicularly
relative to the organic fibers 18 in other layers 32. In this regard, the organic
fibers 18 in any layer 32 may be oriented in any direction relative to one another
including non-uniform arrangements of the organic fibers 18 within a layer 32. Furthermore,
the organic fibers 18 in a layer 32 may be arranged in a woven configuration (not
shown) or in a non-woven configuration such as that which is illustrated in Figures
1-4. The organic fibers 18 of one or more layers 32 may be arranged to be in contacting
or non-contacting arrangement with the organic fibers 18 of adjacent layers 32. For
example, Figure 4 illustrates the layers 32 of organic fibers 18 arranged in non-contacting
relationship with one another such that the layers 32 are separated by matrix 16 material.
[0030] Referring to Figure 3, shown is an enlarged perspective illustration of the composite
article 10 illustrating the relative positions of the organic fibers 18 in the plurality
of layers 32. The organic fibers 18 of each layer 32 are illustrated as being oriented
substantially perpendicularly relative to the organic fibers 18 of the immediately
adjacent layers 32. Furthermore, the organic fibers 18 of each layer 32 are oriented
in substantially parallel alignment with adjacent ones of the organic fibers 18 of
the same layer 32. However, Figure 3 is an illustration of a non-limiting embodiment
of the composite article 10 in a panel 14 configuration and is not to be construed
as limiting alternative configurations of the composite article 10 or alternative
arrangements of the organic fibers 18 within the polymeric matrix 16 of the composite
article 10. For example, the organic fibers 18 of one layer 32 may be oriented in
perpendicular orientation relative to the organic fibers 18 of an adjacent one of
the layers 32. Furthermore, the organic fibers 18 of one layer 32 may be oriented
at any non-perpendicular angle (e.g., 15°, 22.5°, 45°, 60°, etc.) relative to the
organic fibers 18 of an adjacent one of the layers 32.
[0031] Referring to Figure 4, shown is a cross-sectional illustration of an embodiment of
the composite article 10 illustrating the arrangements of the organic fibers 18 in
the layers 32. As can be seen in Figure 4, the organic fibers 18 preferably have an
elongated cross-sectional shape with relatively flattened or substantially planar
fiber faces 20 to minimize scattering of light that may otherwise occur when light
passes through a curved surface. Advantageously, the substantially planar configuration
of the fiber faces 20 of the organic fibers 18 minimizes scattering of light and improves
the optical quality of the composite article 10. The above-mentioned substantially
equivalent temperature coefficients of refractive index of the organic fiber 18 and
polymeric matrix 16 mitigate reductions in optical quality due to temperature change
as described in greater detail below.
[0032] Referring still to Figure 4, the generally elongated shape of the organic fibers
18 preferably includes a relatively high aspect ratio defined as the ratio of fiber
width 28 to fiber thickness 26. In an embodiment, the aspect ratio may vary from approximately
3 to approximately 500 although the fiber 18 cross section may have an aspect ratio
of any value. In an embodiment, the fiber thickness 26 may be in the range from approximately
5 microns to approximately 5,000 microns (0.0002 to 0.20 inch). However, the organic
fiber 18 may be provided in any fiber thickness 26, without limitation.
[0033] Referring to Figure 4, the elongated cross-sectional shape of the organic fibers
18 may include the pair of substantially planar fiber faces 20 which are preferably
oriented substantially parallel to the article surface 12 of the composite article
10. However, the organic fibers 18 may be embedded within the matrix 16 such that
the fiber faces 20 of the organic fiber 18 are arranged in any degree of orientation
relative the article surface 12. Although illustrated as being substantially planar,
the fiber faces 20 of the organic fibers 18 may be slightly curved including slightly
concave, slightly convex or crowned and are not limited to a strictly substantially
planar or flat profile. Even further, it is contemplated that the fiber faces 20 of
the organic fibers 18 may include one or more surface features (not shown) on one
or more of the fiber faces 20.
[0034] As can be seen in Figure 4, the organic fibers 18 within a given layer 32 may be
embedded within the matrix 16 at a desired fiber spacing 34. For example, the organic
fibers 18 may be arranged at a fiber spacing 34 of up to approximately 5,000 microns
(approximately 0.20 inch) or greater. The fiber spacing 34 may be defined as an average
lateral distance between the side edges 22 of adjacent ones of the organic fibers
18 along the length of the organic fibers 18 within a given layer 32. In addition,
the organic fibers 18 may be arranged such that opposing side edges 22 of an adjacent
pair of organic fibers 18 are in contacting relation with one another. However, the
organic fibers 18 are preferably arranged as illustrated in Figure 4 wherein the side
edges 22 are located in spaced relation with one another. In this regard, the organic
fibers 18 may be arranged at any fiber spacing 34 and are not limited to the fiber
spacing 34 illustrated in Figure 4.
[0035] Referring still to Figure 4, the total volume of the organic fibers 18 relative to
the total volume of the composite article 10 may be in the range of from approximately
10% to 90%. However, the organic fibers 18 may comprise any portion of the total volume
of the composite article 10. The desired fiber volume may be selected based on a variety
of parameters including, but not limited to, desired optical properties, desired strength
properties, desired ballistic properties, desired stiffness, and weight requirements
of the composite article 10.
[0036] Although Figure 4 illustrates an elongated configuration for the organic fiber 18
cross section, the organic fiber 18 may be provided in any one of a variety of alternative
cross-sectional shapes. For example, the organic fibers 18 may be formed in any cross-sectional
shape including, but not limited to, a polygon, a quadrilateral, a square, a rectangle
and any other suitable shape. In addition, the cross sections of the organic fibers
18 may include one or more fiber faces 20 that are curved or which include curved
portions as mentioned above. In an embodiment, the cross sections of the organic fibers
18 are preferably elongated as illustrated in Figure 4 with an aspect ratio (e.g.,
ratio of fiber width 28 to fiber thickness 26) of between approximately 3 and 500
although the organic fibers 18 may be provided in any aspect ratio as was indicated
above.
[0037] Referring to Figure 5, shown is a graph of plots of refractive index at a particular
wavelength versus temperature for a polymeric matrix 16, organic fiber 18 and glass
fiber 54. As can be seen in Figure 5, the refractive indices 52, 50 of the matrix
16 and the organic fiber 18 are preferably substantially equivalent within a temperature
range. For example, the graph of Figure 5 illustrates the refractive indices 52, 50
of the matrix 16 and the organic fiber 18 as generally decreasing with increasing
temperature. In a non-limiting embodiment of the present disclosure, the refractive
indices 52, 50 of the matrix 16 and the organic fiber 18 may be selected to be substantially
equivalent within a temperature range of from approximately -65°F to approximately
220°F. However, Figure 5 is representative of one embodiment of matrix 16 and organic
fiber 18 and is not to be construed as limiting alternative embodiments of the matrix
16 and organic fibers 18 which may have refractive indices that vary with temperature
in a manner that is different from that which is illustrated in Figure 5.
[0038] As indicated above, in a preferred embodiment, the matrix 16 and organic fiber 18
may be described as having substantially equivalent refractive indices for a selected
wavelength band of interest for a given temperature range to which the composite article
10 may be subjected. The wavelength band of interest may comprise any spectrum including
the infrared spectrum which may span from approximately 760 nanometers (nm) to 2,500
nm (i.e., frequency of approximately 120 to 400 THz). Additionally, the wavelength
band of interest to which the composite article 10 may be subjected may include the
visible spectrum spanning from approximately 380 nm to 760 nm (i.e., frequency of
approximately 790 to 400 THz). The matrix 16 and organic fiber 18 compositions may
be selected such that the refractive indices of the matrix 16 and organic fiber 18
are substantially equivalent within a temperature range for a selected wavelength
band. For example, the matrix 16 and organic fiber 18 compositions may be selected
such that the refractive indices are substantially equivalent within the ultraviolet
spectrum.
[0039] As was earlier indicated, the refractive indices 52, 50 of the matrix 16 and the
organic fiber 18 are selected such that the refractive indices 52, 50 are maintained
within a predetermined maximum difference from one another for a given temperature
range. For example, the matrix 16 and the organic fiber 18 may be selected such that
the refractive indices 52, 50 are maintained within at least approximately 1 to 3
percent of one another for a given temperature range and a given wavelength band of
interest. In a non-limiting embodiment, the given temperature range wherein the refractive
indices 52, 50 are maintained within at least approximately 1 to 3 percent of one
another may extend from approximately -65°F to approximately 220°F although the temperature
may extend between any range. Likewise, the wavelength band of interest wherein the
refractive indices 52, 50 are maintained within at least approximately 1 to 3 percent
of one another may comprise the visible spectrum and/or the infrared spectrum although
the wavelength band of interest may comprise any spectrum.
[0040] In an embodiment, the refractive indices 52, 50 of the matrix 16 and the organic
fiber 18 may be selected such that the refractive indices 52, 50 are substantially
equivalent for a temperature range in the visible spectrum and/or the infrared spectrum.
Additionally, the refractive indices 52, 50 of the matrix 16 and the organic fiber
18 may be equivalent or, more preferably, identical for at least one temperature match
point 56 within a given temperature range. For example, Figure 5 illustrates a match
point 56 temperature wherein the refractive index 52 of the matrix 16 matches the
refractive index 50 of the organic fiber 18 at the intersection of the refractive
index curves 52, 50 of the matrix 16 and the organic fiber 18.
[0041] However, Figure 5 is representative of one embodiment of matrix 16 material and organic
fiber 18 material and is not to be construed as limiting alternative materials which
may have different refractive indices that may not necessarily match within a given
temperature range for a given wavelength. Notably, Figure 5 illustrates that the refractive
indices 52, 50 of the matrix 16 and the organic fiber 18 are substantially equivalent
along a temperature range as compared to the refractive index 54 of the glass fiber
54 which is relatively constant or slight in variation and therefore results in a
relatively large divergence with the matrix refractive index 52 of the polymeric matrix
16 as temperature increases or decreases.
[0042] As indicated above, the matrix 16 and organic fibers 18 preferably have substantially
equivalent temperature coefficients of refractive index. In an embodiment, the organic
fiber 18 and the matrix 16 may be selected to have any suitable temperature coefficients
of refractive index. Figure 5 illustrates the refractive index 52, 50 of the matrix
16 and organic fiber 18 decreasing with increasing temperature. The relatively small
difference in the refractive index 52, 50 of the matrix 16 and organic fiber 18 minimizes
optical distortion as the temperature of the composite article 10 changes.
[0043] Referring to Figure 6, shown is a graph illustrating the mechanical performance of
composite articles 10' comprised of organic fibers 62 embedded within polymeric matrix
16 (Figures 1-4) in a cross-ply configuration wherein the organic fibers 18 (Figure
3) in a layer 32 (Figure 3) may be oriented generally perpendicularly relative to
the organic fibers 18 in other layers 32 similar to the organic fiber 18 arrangement
illustrated in Figure 3. Figure 6 plots the strength 58 (in ksi) and modulus of elasticity
60 (in Msi) for the composite articles 10' of different compositions. Figure 6 also
graphically illustrates that the strength properties of a composite article 10' comprised
of glass fiber 66 has strength 58 values that may be generally comparable to a composite
article 10' comprised of organic fiber 62. Furthermore, Figure 6 illustrates the composite
article 10' comprised of glass fiber 66 as having a generally higher modulus of elasticity
60 than certain compositions of the organic fiber 62. However, as was earlier indicated,
the temperature coefficient of refractive index of glass fiber 54 is substantially
different than the temperature coefficient of refractive index of polymeric matrix
52 as illustrated in Figure 5 which may result in increasingly poor optical quality
of a glass fiber-reinforced polymer matrix composite article 10 as the temperature
of the composite article 10 changes.
[0044] Figure 6 illustrates strength 58 (in ksi) and modulus of elasticity 60 (in Msi) for
composite articles 10' (Figures 1-4) having organic fibers 62 of different compositions.
For comparison, Figure 6 also illustrates the mechanical properties for a composite
article comprised of polymers 76 (i.e., polymeric material) without organic fibers
for reinforcing. As can be seen in Figure 6, the composite article 10' comprised of
polymers 76 without organic fibers 62 may have a tensile strength 58 in the range
of from approximately 6 ksi to approximately 20 ksi and a modulus of elasticity 60
in the range of from approximately 0.2 Msi to approximately 0.55 Msi. In contrast,
a composite article 10' comprising polymer matrix reinforced with fluorocarbon fiber
68 as the organic fiber 62 may have a tensile strength 58 in the range of from approximately
6 ksi to approximately 62 ksi and a modulus of elasticity 60 in the range of from
approximately 0.1 Msi to approximately 0.3 Msi. A composite article 10' comprising
Nylon
™ fiber 70 may have a tensile strength 58 in the range of from approximately 6 ksi
to approximately 78 ksi and a modulus of elasticity 60 in the range of from approximately
0.2 Msi to approximately 0.5 Msi.
[0045] Referring still to Figure 6, also shown is a composite article 10' comprising polypropylene
fiber 74 and having a tensile strength 58 in the range of from approximately 6 ksi
to approximately 80 ksi and a modulus of elasticity 60 in the range of from approximately
0.45 Msi to approximately 1.1 Msi. A composite article 10' comprising polyethylene
terephthalate fiber 72 may have a tensile strength 58 in the range of from approximately
6 ksi to approximately 70 ksi and a modulus of elasticity 60 in the range of from
approximately 0.4 Msi to approximately 0.8 Msi. A composite article 10' comprising
polyethylene fiber 64 may have a tensile strength 58 in the range of from approximately
10 ksi to approximately 300 ksi and a modulus of elasticity 60 in the range of from
approximately 0.5 Msi to approximately 9.0 Msi.
[0046] As can be seen in Figure 6, the composite article 10' comprised of polyethylene fiber
64 exhibits improved strength 58 and superior stiffness (i.e., modulus of elasticity
60) relative to a composite article 10' comprising glass fibers 66. More particularly,
Figure 6 illustrates that a composite article 10' comprising polyethylene fiber 64
may have a tensile strength 58 in the range of from approximately 10 ksi to approximately
300 ksi and a modulus of elasticity 60 in the range of from approximately 0.5 Msi
to approximately 9.0 Msi. In contrast, the composite article 10' comprising glass
fibers 66 is illustrated as having a tensile strength 58 in the range of from approximately
28 ksi to approximately 75 ksi and a modulus of elasticity 60 of from approximately
1.2 Msi to approximately 2.7 Msi. It should be noted that the above-recited values
for the strength 58 (in ksi) and modulus of elasticity 60 (in Msi) for composite articles
10' comprised of organic fibers 62 are non-limiting examples and that higher values
for the strength 58 (in ksi) and modulus of elasticity 60 (in Msi) are possible.
[0047] The polyethylene fiber 64 may comprise a stretched polyethylene fiber 64 configuration
having improved tensile strength 58 relative to other fiber materials. The stretching
of the polyethylene fiber 64 may facilitate alignment of the fiber molecules resulting
in an increase in tensile strength and stiffness of the polyethylene fiber 64 which,
when embedded within the matrix 16 of the composite article 10 (Figures 1-4), results
in improved specific performance of the composite article 10'. For example, as indicated
above, the polyethylene fiber 64 may result in an increase in specific stiffness of
the composite article 10' relative to the specific stiffness of a composite article
10' fabricated with glass fiber 66.
[0048] As may be appreciated, the optical and mechanical performance of the composite article
10 (Figures 1-4) may be dependent in part upon the composition of the matrix 16 material
and the organic fiber 18. The matrix 16 and the organic fiber 18 materials may be
selected based on the intended application of the composite article 10 (Figures 1-4).
Materials from which the organic fiber 18 may be formed include, without limitation,
any suitable thermoplastic or thermosetting material. For example, thermoplastic material
from which the matrix 16 and/or the organic fiber 18 may be formed include, without
limitation, fluorocarbons, polyamides, polyethylenes, polyesters, polypropylenes,
polycarbonates, polyurethanes, polyetheretherketone, polyetherketoneketone. Polyethylenes
may include ultra high molecular weight polyethylene, high density polyethylene, or
any other form of polyethylene including any other molecular weight of polyethylene.
The thermoplastic material may also include Nylon
™ and any one of a variety of other substantially transparent organic materials or
combinations thereof. Thermosets from which the matrix 16 and/or the organic fiber
18 may be formed may include, without limitation, polyurethanes, phenolics, polyimides,
bismaleimides, polyesters, epoxies, and any one of a variety of any other suitable
transparent polymeric materials.
[0049] As indicated earlier, selection of the materials for the matrix 16 (Figures 1-4)
and organic fiber 18 as well as selection of the organic fiber 18 geometry and arrangement
including fiber shape, fiber thickness 26 (Figure 4), fiber width 28 (Figure 4), fiber
spacing 34 (Figure 4), layer spacing 36 (Figure 4) and fiber volume may be based in
part upon the environment (for example, temperature range and wavelength band of interest)
to which the composite article 10 (Figure 1) may be subjected. The composite article
10 may be configured in any one of a variety of configurations including the panel
14 configuration (Figure 1) or any one of a variety of alternative configurations
including, but not limited to, as a transparency of a vehicle such as a windshield
and/or a canopy of an aircraft. In addition, the composite article 10 may be configured
for use in any vehicular or non-vehicular application such as a structural panel or
architectural panel for a building or structure or for a non-structural application.
In this regard, the composite article 10 may be configured for use in any application,
system, subsystem, structure, apparatus and/or device, without limitation.
[0050] Referring now to Figure 7, shown is an illustration of a flowchart of one or more
operations that may comprise a methodology of manufacturing a composite article 10
(Figure 1). Step 100 of the methodology may include selecting a wavelength band of
interest to which the composite article 10 may be subjected. For example, step 100
may include selecting the visible spectrum and/or the infrared spectrum of radiation
to which the composite article 10 may be subjected. As was indicated earlier, in addition
to varying with temperature, the refractive index of a material may also vary with
the wavelength of radiation to which the material is subjected.
Step 102 of Figure 7 may comprise selecting the temperature range within which the
composite article 10 may be subjected. For example, the temperature range of the composite
article 10 (Figure 1) may extend from approximately -65°F to approximately 220°F.
However, depending upon the application, the operating temperature ranges of the composite
article 10 may extend from approximately -65°F to 180°F, from approximately -65°F
to 160°F, from approximately -40°F to 160°F, or from approximately 0°F to 130°F. However,
the temperature range may extend between any set of temperatures including temperatures
below -65°F and/or temperatures above 220°F and is not limited to the above-mentioned
ranges.
[0051] As was indicated earlier, the refractive index of polymeric matrix 52 and organic
fiber 50 may generally decrease with increasing temperature. The polymeric matrix
16 material may be selected such that the refractive index of the matrix 16 matches
the refractive index of the organic fiber 18 at a match point 56 (Figure 5) within
the temperature range. In this manner, differences in refractive index between the
matrix 16 and organic fiber 18 may be minimized as the temperature diverges (i.e.,
increases or decreases) from the match point 56 temperature. However, as was earlier
indicated, the refractive index of the matrix 16 and organic fiber 18 may not necessarily
match at any specific temperature within the temperature operating range.
Step 104 of the methodology of Figure 7 may comprise providing a substantially transparent
matrix 16 (Figures 1-4) having a matrix refractive index 52 and a temperature coefficient
of refractive index. The matrix 16 may comprise any suitable matrix 16 for a given
application. For example, as indicated above, the matrix 16 may comprise any suitable
thermoplastic material or any suitable thermoset. Non-limiting examples of thermoplastic
materials include the above-mentioned Nylon™, fluorocarbons, polyamides, polyethylenes, polyesters, polypropylenes, polycarbonates,
polyurethanes, polyetheretherketone, polyetherketoneketone. Non-limiting examples
of thermosets may include polyurethanes, phenolics, polyimides, bismaleimides, polyesters,
and epoxies.
Step 106 of Figure 7 may comprise providing at least one substantially transparent
organic fiber 18 (Figures 1-4) having a refractive index 50 and a temperature coefficient
of refractive index. The organic fiber 18 preferably has a refractive index 50 that
is substantially equivalent to the matrix refractive index 52 within the wavelength
band of interest. The matrix 16 may be selected such that the refractive index 52
of the matrix 16 is within a predetermined maximum difference relative to the refractive
index 50 of the fiber 18 for a given temperature range. For example, the matrix 16
and the organic fiber 18 may be selected such that the refractive indices 52, 50,
thereof, are within approximately 1 percent to approximately 3 percent of one another
for any suitable temperature range such as in the temperature range of from approximately
-65°F to approximately 220°F. However, the refractive indices 52, 50 of the matrix
16 and the organic fiber 18 may be within any range of one another. For example, the
refractive indices 52, 50 of the matrix 16 and the organic fiber 18 may differ from
one another by greater than 3 percent. Additionally, the refractive indices 52, 50
of the matrix 16 and the organic fiber 18 may be within approximately 1 percent to
0.3 percent or less of one another. Furthermore, the temperature range for any of
the above-noted differences in refractive indices 52, 50 of the matrix 16 and the
organic fiber 18 may extend between any set of temperatures, without limitation.
[0052] The selection of the organic fiber 18 (Figures 1-4) in Step 106 may further comprise
selecting the organic fiber 18 such that the temperature coefficient of refractive
index thereof is substantially equivalent to the temperature coefficient of refractive
index of the matrix 16. Advantageously, by selecting the matrix 16 and organic fiber
18 such that the temperature coefficients of refractive index are substantially equivalent,
differences in refractive indices in the matrix 16 and organic fiber 18 may be minimized
when temperature increases or decreases. For example, Figure 5 illustrates that the
refractive indices 52, 50 of the matrix 16 and the organic fiber 18 are substantially
equivalent within a temperature range which results in a relatively small divergence
in the matrix 52 and organic fiber 50 refractive indices.
[0053] Referring still to Figure 7, Step 108 may comprise providing the organic fiber 18
in an elongated cross-sectional shape having an opposing pair of substantially planar
fiber faces 20 (Figure 4) which may preferably be oriented substantially parallel
to an article surface 12 of the composite article 10 as illustrated in Figure 4. However,
the organic fiber 18 may be oriented such that the fiber faces 20 are oriented in
non-parallel arrangement (not shown) relative to the article surfaces 12 of the composite
article 10. Preferably, the organic fiber 18 (Figure 4) has an approximately rectangular
cross-sectional shape having opposing substantially planar fiber faces 20 that are
substantially parallel to one another along a through-thickness direction of the organic
fiber 18. However, as was indicated above, the organic fiber 18 may be provided in
any suitable configuration and is not limited to an elongated or rectangular cross-sectional
shape.
Step 110 of the methodology of Figure 7 may include embedding a plurality of the organic
fibers 18 within the matrix 16 as shown in Figure 4. In an embodiment, the plurality
of organic fibers 18 may be arranged in the layer 32 configuration as illustrated
in Figures 2-5. The organic fibers 18 within each layer 32 may be spaced at a desired
fiber spacing 34 defined as an average lateral distance between the fiber edges 22
of adjacent ones of the organic fibers 18 in a given layer 32 as illustrated in Figure
4. The organic fibers 18 in adjacent ones of the layers 32 may be arranged such that
the axes 30 (Figure 3) of the organic fibers 18 in one layer 32 are oriented at a
predetermined angle such as at an approximate 90° angle relative to the fiber axes
30 of the organic fibers 18 of immediately adjacent layers 32 as illustrated in Figure
3. However, the axes 30 of the organic fibers 18 in one layer 32 may be oriented at
any one of a variety of alternative angles relative to the fiber axes 30 of the organic
fibers 18 of immediately adjacent layers 32. For example, the axes 30 of the organic
fibers 18 in one layer 32 may be oriented at any non-perpendicular angle (e.g., 15°,
22.5°, 45°, 60°, etc.) relative to the fiber axes 30 of the organic fibers 18 of immediately
adjacent layers 32.
Step 112 of the methodology of Figure 7 may comprise orienting the fiber faces 20
(Figure 4) of the organic fibers 18 to be substantially parallel to the article surface
12 of the composite article 10 to maintain optical clarity of the composite article
10. The organic fibers 18 may be provided in any suitable cross-sectional shape as
indicated above and in any suitable fiber volume relative to the total volume of the
composite article 10. Advantageously, the substantially equivalent refractive indices
of the matrix 16 and the organic fiber 18 within a range of temperatures improves
optical transmission and minimizes distortion of the composite article 10.
[0054] In a preferred embodiment, a composite article, comprises a substantially transparent
matrix having a matrix refractive index, and at least one substantially transparent
organic fiber embedded within the matrix, the organic fiber having a refractive index
that is substantially equivalent to the matrix refractive index within a wavelength
band of interest. The composite article may further comprise the matrix and the organic
fiber have substantially equivalent temperature coefficients of refractive index.
The composite article may further comprise the refractive indices and the temperature
coefficients of refractive index of the matrix and the organic fiber are such that
the refractive indices of the matrix and the organic fiber are equivalent at a given
wavelength within the wavelength band of interest for at least one temperature within
a temperature range. The composite article may further comprise the refractive indices
and the temperature coefficients of refractive index of the matrix and the organic
fiber are such that the refractive indices of the matrix and the organic fiber are
within approximately 1 to 3 percent of one another within the wavelength band of interest
for a temperature range of from approximately -65°F to approximately 220°F. The composite
article may further comprise the wavelength band of interest comprises at least one
of the infrared spectrum and the visible spectrum. The composite article may further
comprise the organic fiber has an elongated cross section. The composite article may
further comprise the cross section has an aspect ratio of fiber width to fiber thickness;
and the aspect ratio being in the range of from approximately 3 to approximately 500.
The composite article may further comprise the fiber thickness is in the range of
from approximately 5 microns to approximately 5000 microns. The composite article
may further comprise the organic fiber has an opposing pair of substantially planar
fiber faces being substantially parallel to one another. The composite article may
further comprise the substantially planar fiber faces are substantially parallel to
a substantially planar article surface of the composite article. The composite article
may further comprise wherein at least one of the matrix and the organic fiber are
formed from at least one of the following: a thermoplastic material; anda thermoset.
The composite article may further comprise the thermoplastic material comprises at
least one of the following: fluorocarbons, polyamides, polyethylenes, polypropylenes,
polycarbonates, polyurethanes, polyetheretherketone, polyetherketoneketone; and the
thermoset comprises at least one of the following: polyurethanes, phenolics, polyimides,
bismaleimides, polyesters, epoxy. The composite article may form a sturcutre such
as a windshield, a canopy, a window, a membrane, a structural panel, an architectural
panel, a non-structural article.
[0055] In another preferred embodiment a substantially optically transparent composite article
may comprise, a substantially transparent matrix having a matrix refractive index,
a plurality of substantially transparent organic fibers embedded within the matrix,
the organic fibers having a refractive index that is substantially equivalent to the
matrix refractive index within at least one of the visible spectrum and the infrared
spectrum, and the matrix and the organic fibers having substantially equivalent temperature
coefficients of refractive index.
[0056] In another preferred embodiment a method of manufacturing a composite article, may
comprise providing a substantially transparent matrix having a matrix refractive index,
providing at least one substantially transparent organic fiber having a refractive
index that is substantially equivalent to the matrix refractive index, and embedding
the organic fiber within the matrix. The method may further comprise selecting a wavelength
band of interest and selecting the matrix and the organic fiber such that a temperature
coefficient of refractive index of the matrix is substantially equivalent to a temperature
coefficient of refractive index of the fiber within the wavelength band of interest.
The method may further comprise selecting the matrix and the organic fiber such that
the refractive indices thereof are equivalent at a given wavelength within the wavelength
band of interest for at least one temperature within a temperature range. The method
may further comprise selecting the matrix and the organic fiber such that the refractive
indices thereof are within approximately 1 to 3 percent of one another for the temperature
range of from approximately -65°F to approximately 220°F. The method may further comprise
selecting at least one of the infrared spectrum and the visible spectrum as the wavelength
band of interest. The method may further comprise providing the organic fiber in an
elongated cross section. The method may further comprise providing the organic fiber
in a cross section having an opposing pair of the substantially planar faces oriented
substantially parallel to one another. The method may further comprise orienting the
fiber such that the substantially planar faces of the fiber cross section are substantially
parallel to a substantially planar article surface of the composite article. The method
may further comprise a thermoplastic material and a thermoset. The method may further
comprise the thermoplastic material comprises at least one of the following: fluorocarbons,
polyamides, polyethylenes, polyesters, polypropylenes, polycarbonates, polyurethanes,
polyetheretherketone, polyetherketoneketone, and the thermoset comprises at least
one of the following: polyurethanes, phenolics, polyimides, bismaleimides, polyesters,
epoxy.
[0057] In another preferred emobodiment a method of manufacturing a composite article, may
comprise the steps of selecting at least one of a visible spectrum and an infrared
spectrum as a wavelength band of interest to which the composite article is to be
subjected; selecting a temperature range to which the composite article is to be subjected;
providing a substantially transparent matrix having a matrix refractive index and
a temperature coefficient of refractive index; providing a plurality of substantially
transparent organic fibers having a refractive index and a temperature coefficient
of refractive index that is substantially equivalent to the temperature coefficient
of refractive index of the matrix within the temperature range, the refractive index
of the fibers being substantially equivalent to the matrix refractive index within
the wavelength band of interest; providing the organic fibers in an elongated cross
section having an opposing pair of substantially planar fiber faces; embedding the
organic fibers within the matrix to form at least one layer of organic fibers within
the matrix; and orienting the substantially planar fiber faces to be substantially
parallel to a substantially planar article surface of the composite article.
1. A composite article (10), comprising:
a substantially transparent matrix (16) having a matrix refractive index (52); and
a plurality of substantially transparent organic fibers (18) embedded within the matrix,
the organic fibers having a refractive index (50) and a temperature coefficient of
refractive index such that the refractive indices (50, 52) of the matrix and the organic
fibers are within approximately 1 to 3 percent of one another within a wavelength
band of interest for a temperature range of from approximately -65°F to approximately
220°F (-54°C to 104°C);
wherein the organic fibers (18) are formed as strips and arranged in layers (32) within
the matrix (16), each of the organic fibers (18) having an elongated cross-sectional
shape including an opposed pair of substantially planar fiber faces (20), the fiber
faces being substantially parallel to a substantially planar article surface (12)
of the composite article; and
wherein the layers (32) of organic fibers (18) are arranged in non-contacting relationship
with one another such that the layers (32) are separated by matrix material (16),
the organic fibers (18) in each one of the layers (32) being aligned with one another
in substantially parallel relationship, and the organic fibers (18) in adjacent ones
of the layers (32) being oriented at a predetermined angle relative to the fiber axes
(30) of the organic fibers of immediately adjacent layers (32).
2. The composite article of Claim 1 wherein the predetermined angle is 90°.
3. The composite article of Claim 1 wherein the predetermined angle is a non-perpendicular
angle such as 15°, 22.5°, 45° or 60°.
4. The composite article of Claim 1 wherein the wavelength band of interest comprises
one of the visible spectrum, the infrared spectrum and the ultraviolet spectrum.
5. The composite article of Claim 1 wherein the elongated cross-sectional shape of the
organic fibers has an aspect ratio of fiber width (28) to fiber thickness (26), and
the aspect ratio is in the range of from approximately 3 to approximately 500.
6. The composite article of Claim 5 wherein the fiber thickness is in the range of from
approximately 5 microns to approximately 5000 microns.
7. The composite article of Claim 1, wherein at least one of the matrix and the organic
fiber are formed from at least one of the following:
a thermoplastic material comprises at least one of the following: fluorocarbons, polyamides,
polyethylenes, polypropylenes, polycarbonates, polyurethanes, polyetheretherketone,
polyetherketoneketone; and
a thermoset comprises at least one of the following: polyurethanes, phenolics, polyimides,
bismaleimides, polyesters, epoxy.
8. A method of manufacturing a composite article (10), comprising the steps of:
providing (104) a substantially transparent matrix (16) having a matrix refractive
index (52);
providing (106) a plurality of substantially transparent organic fibers (18) having
a refractive index (50) and a temperature coefficient of refractive index such that
the refractive indices (50, 52) of the matrix and the organic fibers are within approximately
1 to 3 percent of one another within a wavelength band of interest for a temperature
range of from approximately -65°F to approximately 220°F (-54°C to 104°C); and
embedding (110) the organic fiber within the matrix;
wherein the organic fibers (18) are formed as strips and arranged in layers (32) within
the matrix (16), each of the organic fibers (18) having an elongated cross-sectional
shape including an opposed pair of substantially planar fiber faces (20), the fiber
faces being substantially parallel to a substantially planar article surface (12)
of the composite article; and
wherein the layers (32) of organic fibers (18) are arranged in non-contacting relationship
with one another such that the layers (32) are separated by matrix material (16),
the organic fibers (18) in each one of the layers being aligned with one another in
substantially parallel relationship, and the organic fibers (18) in adjacent ones
of the layers (32) being oriented at a predetermined angle relative to the fiber axes
(30) of the organic fibers of immediately adjacent layers (32).
9. The method of Claim 8 wherein at least one of the matrix and the organic fiber is
formed from at least one of the following:
a thermoplastic material comprises at least one of the following: fluorocarbons, polyamides,
polyethylenes, polyesters, polypropylenes, polycarbonates, polyurethanes, polyetheretherketone,
polyetherketoneketone; and
a thermoset comprises at least one of the following: polyurethanes, phenolics, polyimides,
bismaleimides, polyesters, epoxy.
1. Verbundartikel (10), der aufweist:
eine im Wesentlichen transparente Matrix (16), die eine Matrixbrechzahl (52) aufweist;
und
mehrere im Wesentlichen transparente organische Fasern (18), die in der Matrix eingebettet
sind, wobei die organischen Fasern eine solche Faserbrechzahl (50) und einen solchen
Temperaturkoeffizienten der Brechzahl aufweisen, dass die Brechzahlen (50, 52) der
Matrix und der organischen Fasern innerhalb eines interessierenden Wellenlängenbereichs
in einem Temperaturbereich von etwa -65 °F bis etwa 220 °F (-54 °C bis 104 °C) nicht
mehr als in etwa 1 bis 3 Prozent voneinander abweichen;
wobei die organischen Fasern (18) als Streifen ausgebildet und innerhalb der Matrix
(16) in Lagen (32) angeordnet sind, wobei jede der organischen Fasern (18) einen länglichen
Querschnitt ausweist und ein gegenüberliegendes Paar von im Wesentlichen planaren
Faserflächen (20) umfasst, wobei die Faserflächen im Wesentlichen parallel zu einer
im Wesentlichen planaren Artikelfläche (12) des Verbundartikels verlaufen; und
wobei die Lagen (32) der organischen Fasern (18) so zueinander angeordnet sind, dass
sie sich nicht berühren und die Lagen (32) durch Matrixmaterial (16) getrennt sind,
wobei die organischen Fasern (18) in jeder der Lagen (32) in etwa parallel zueinander
ausgerichtet sind und die organischen Fasern (18) in benachbarten Lagen (32) in Bezug
auf die Faseraxen (30) der organischen Fasern der unmittelbar benachbarten Lagen (32)
in einem vorgegebenen Winkel orientiert sind.
2. Verbundartikel nach Anspruch 1, wobei der vorgegebene Winkel 90° beträgt.
3. Verbundartikel nach Anspruch 1, wobei der vorgegebene Winkel nicht rechtwinklig ist
und beispielsweise 15°, 22,5°, 45° oder 60° beträgt.
4. Verbundartikel nach Anspruch 1, wobei der interessierende Wellenlängenbereich den
sichtbaren Bereich, den Infrarotbereich oder den ultravioletten Bereich umfasst.
5. Verbundartikel nach Anspruch 1, wobei der längliche Querschnitt der organischen Fasern
ein Aspektverhältnis der Faserbreite (28) zur Faserdicke (26) aufweist und das Aspektverhältnis
im Bereich von etwa 3 bis etwa 500 liegt.
6. Verbundartikel nach Anspruch 5, wobei die Faserdicke im Bereich von etwa 5 bis etwa
5000 Mikrometern liegt.
7. Verbundartikel nach Anspruch 1, wobei die Matrix und/oder die organische Faser aus
zumindest einem der folgenden Materialien gebildet sind:
einem thermoplastischen Material, das zumindest einen der folgenden Stoffe umfasst:
Fluorkohlenwasserstoffe, Polyamide, Polyethylene, Polypropylene, Polycarbonate, Polyurethane,
Polyetheretherketone, Polyetherketonketone; und
einem duroplastischen Material, das zumindest einen der folgenden Stoffe umfasst:
Polyurethane, Phenole, Polyimide, Bismaleimide, Polyester, Epoxide.
8. Verfahren zur Herstellung eines Verbundartikels (10), das Schritte aufweist zum:
Bereitstellen (104) einer im Wesentlichen transparenten Matrix (16), die eine Matrixbrechzahl
(52) aufweist; und
Bereitstellen (106) von mehreren im Wesentlichen transparenten organischen Fasern
(18), die eine solche Faserbrechzahl (50) und einen solchen Temperaturkoeffizienten
der Brechzahl aufweisen, dass die Brechzahlen (50, 52) der Matrix und der organischen
Fasern innerhalb eines interessierenden Wellenlängenbereichs in einem Temperaturbereich
von etwa -65 °F bis etwa 220 °F (-54 °C bis 104 °C) nicht mehr als in etwa 1 bis 3
Prozent voneinander abweichen; und
Einbetten (110) der organischen Fasern in der Matrix; wobei die organischen Fasern
(18) als Streifen ausgebildet und innerhalb der Matrix (16) in Lagen (32) angeordnet
sind, wobei jede der organischen Fasern (18) einen länglichen Querschnitt ausweist
und ein gegenüberliegendes Paar von im Wesentlichen planaren Faserflächen (20) umfasst,
wobei die Faserflächen im Wesentlichen parallel zu einer im Wesentlichen planaren
Artikelfläche (12) des Verbundartikels verlaufen; und
wobei die Lagen (32) der organischen Fasern (18) so zueinander angeordnet sind, dass
sie sich nicht berühren und die Lagen (32) durch Matrixmaterial (16) getrennt sind,
wobei die organischen Fasern (18) in jeder der Lagen (32) in etwa parallel zueinander
ausgerichtet sind und die organischen Fasern (18) in benachbarten Lagen (32) in Bezug
auf die Faseraxen (30) der organischen Fasern der unmittelbar benachbarten Lagen (32)
in einem vorgegebenen Winkel orientiert sind.
9. Verfahren nach Anspruch 8, wobei die Matrix und/oder die organische Faser aus zumindest
einem der folgenden Materialien gebildet sind:
einem thermoplastischen Material, das zumindest einen der folgenden Stoffe umfasst:
Fluorkohlenwasserstoffe, Polyamide, Polyethylene, Polyester, Polypropylene, Polycarbonate,
Polyurethane, Polyetheretherketone, Polyetherketonketone; und
einem duroplastischen Material, das zumindest einen der folgenden Stoffe umfasst:
Polyurethane, Phenole, Polyimide, Bismaleimide, Polyester, Epoxide.
1. Article composite (10), comprenant :
une matrice (16) sensiblement transparente ayant un indice de réfraction (52) de la
matrice ; et
une pluralité de fibres organiques (18) sensiblement transparentes incorporées dans
la matrice, les fibres organiques ayant un indice de réfraction (50) et un coefficient
de température de l'indice de réfraction tel que les indices de réfraction (50, 52)
de la matrice et des fibres organiques sont de l'ordre d'environ 1 à 3 % l'un par
rapport à l'autre dans une bande de longueur d'onde d'intérêt pour une plage de température
d'environ -65 °F à environ 220 °F (-54 °C à 104 °C) ;
dans lequel les fibres organiques (18) sont formées sous forme de bandes et arrangées
en couches (32) dans la matrice (16), chaque fibre organique (18) ayant une forme
transversale allongée incluant une paire opposée de faces de fibre (20) sensiblement
planaires, les faces de fibre étant sensiblement parallèles à une surface de l'article
(12) sensiblement planaire de l'article composite ; et
dans lequel les couches (32) des fibres organiques (18) sont arrangées selon une relation
sans contact les unes avec les autres de telle sorte que les couches (32) sont séparées
par le matériau matriciel (16), les fibres organiques (18) dans chacune des couches
(32) étant alignées les unes par rapport aux autres selon une relation sensiblement
parallèle, et les fibres organiques (18) dans les couches (32) adjacentes étant orientées
selon un angle prédéterminé par rapport aux axes de fibre (30) des fibres organiques
des couches (32) immédiatement adjacentes.
2. Article composite selon la revendication 1, dans lequel l'angle prédéterminé est de
90°.
3. Article composite selon la revendication 1, dans lequel l'angle prédéterminé est un
angle non perpendiculaire tel que 15°, 22,5°, 45° ou 60°.
4. Article composite selon la revendication 1, dans lequel la bande de longueur d'onde
d'intérêt comprend une bande du spectre visible, du spectre infrarouge et du spectre
ultraviolet.
5. Article composite selon la revendication 1, dans lequel la forme transversale allongée
des fibres organiques a un rapport d'aspect de la largeur des fibres (28) à l'épaisseur
des fibres (26), et le rapport d'aspect est compris dans la plage allant d'environ
3 à environ 500.
6. Article composite selon la revendication 5, dans lequel l'épaisseur des fibres est
comprise dans la plage allant d'environ 5 µm à environ 5000 µm.
7. Article composite selon la revendication 1, dans lequel la matrice et/ou les fibres
organiques sont formées par au moins un des éléments suivants :
un matériau thermoplastique comprenant au moins un des éléments suivants : les fluorocarbures,
les polyamides, les polyéthylènes, les polypropylènes, les polycarbonates, les polyuréthanes,
les polyétheréthercétones, les polyéthercétonecétones ; et
un composé thermodurcissable comprenant au moins un des éléments suivants : les polyuréthanes,
les composés phénoliques, les polyimides, les bismaléimides, les polyesters, les époxy.
8. Procédé de fabrication d'un article composite (10), comprenant les étapes consistant
à :
utiliser (104) une matrice (16) sensiblement transparente ayant un indice de réfraction
(52) de la matrice ; et
utiliser (106) une pluralité de fibres organiques (18) sensiblement transparentes
ayant un indice de réfraction (50) et un coefficient de température de l'indice de
réfraction tel que les indices de réfraction (50, 52) de la matrice et des fibres
organiques sont de l'ordre d'environ 1 à 3 % l'un par rapport à l'autre dans une bonde
de longueur d'onde d'intérêt pour une plage de température d'environ -65 °F à environ
220 °F (-54 °C à 104 °C) ; et
incorporer (110) les fibres organiques dans la matrice ;
dans lequel les fibres organiques (18) sont formées sous forme de bandes et arrangées
en couches (32) dans la matrice (16), chaque fibre organique (18) ayant une forme
transversale allongée incluant une paire opposée de faces de fibre (20) sensiblement
planaires, les faces de fibre étant sensiblement parallèles à une surface de l'article
(12) sensiblement planaire de l'article composite ; et
dans lequel les couches (32) des fibres organiques (18) sont arrangées selon une relation
sans contact les unes avec les autres de telle sorte que les couches (32) sont séparées
par le matériau matriciel (16), les fibres organiques (18) dans chacune des couches
(32) étant alignées les unes par rapport aux autres selon une relation sensiblement
parallèle, et les fibres organiques (18) dans les couches (32) adjacentes étant orientées
selon un angle prédéterminé par rapport aux axes de fibre (30) des fibres organiques
des couches (32) immédiatement adjacentes.
9. Procédé selon la revendication 8, dans lequel la matrice et/ou les fibres organiques
sont formées par au moins un des éléments suivants :
un matériau thermoplastique comprenant au moins un des éléments suivants : les fluorocarbures,
les polyamides, les polyéthylènes, les polypropylènes, les polycarbonates, les polyuréthanes,
les polyétheréthercétones, les polyéthercétonecétones ; et
un composé thermodurcissable comprenant au moins un des éléments suivants : les polyuréthanes,
les composés phénoliques, les polyimides, les bismaléimides, les polyesters, les époxy.